Why Does the Net Still Work on Christmas? Paul Mockapetris

In 1983, you could ask for your own internet address. But not after 6 p.m. California time. Or over the Christmas holiday.

When the internet was still the ARPAnet – the government-funded network that connected various research outfits across the country – you couldn't get an address without the help of Elizabeth "Jake” Feinler and the Stanford Research Institute's Network Information Center. And the NIC wasn't open around the clock.

"If you wanted to add a machine to the network, you had to call SRI, and you would talk to the Network Information Center and ask for a name and an address," says Paul Mockapetris, who worked on the ARPAnet in the early- to mid-'80s as a researcher at the University of Southern California. "The problem is that SRI was off during Christmas week, and they went home on weekdays."

Mockapetris is the man who solved this problem. He invented the Domain Naming System, or DNS, which automated the management of internet names and addresses by spreading the duties among myriad servers setup across the network, and ultimately, it allowed the internet to operate without the NIC or any other single naming authority.

Though the DNS has evolved significantly, the same basic system is still used today, and earlier this year, in recognition of his contribution, Mockapetris was inducted into the inaugural class of the Internet Society’s (ISOC) Internet Hall of Fame, alongside such names as Vint Cerf, Sir Tim Berners-Lee, Van Jacobson, and the woman who preceded him as the grand poobah of internet naming: "Jake” Feinler.

One day, in 1983, Mockapetris was sitting in his office at USC when Jon Postel walked in. Postel has been a part of the research team at another Southern California university – the University of California, Los Angeles – that sent the world's first internet message, and by the early '80s, he had spent a decade overseeing the RFCs, or Request for Comments – the documents that defined how the internet was built.

Postel walked in because he had a job for Mockapetris. He wanted him to find a compromise between five different proposals for improving the way the APRAnet dealt with names and addresses. Mockapetris took the job, but he pretty much ignored the five proposals and built his own system. "I just went off and did my own thing," he says, "and they all thought I didn't use much of their stuff. But by the time, they figured it out, it was what it was." It was DNS.

Previously, the NIC kept track of all the various ARPAnet addresses using a master file called host.text, and Feinler and her cohorts ran a set of central servers that made sure this file was distributed to all the other machines on the network. But with DNS, Mockapetris drew on work he'd done with distributed systems at MIT's Architecture Machine Group, the forerunner of the MIT Media Lab. The system was designed to spread naming duties across a larger number of servers that sat in disparate places across the network.

"You can divide up the responsibility, but still have it all look like one database," Mockapetris says. That way, if one naming server went down, another could help you.

The system ensured that every device on the network knew about every other devices. When you typed in a domain name, it turned that into an internet protocol, or IP, address, where the individual packets should be routed. "In order to do anything on the internet, you have to be able to tell people who you are, and the DNS does that. Plus, it lets you look up anyone who has put their data in the DNS."

But, just as importantly, Mockapetris says, it let you make update your own network without breaking your connection to everyone else. "The big deal," Mockapetris says, "is that it allowed everyone to manage their own networks and change the parameters of their networks and have those changes be visible everywhere."

It was a time when the entire network was morphing into something similar to the network we know today. The APRAnet was moving to the TCP/IP protocol that still underpins the modern internet, and DNS was part of a larger overhaul of the way everything worked. The first DNS specification was finished in 1983. A revised version arrived three years later. And by that year, Mockapetris says, people were relying DNS without using the old master of list of names as a safety net.

Today, the internet spans over 200 million domains, and DNS is still making sure everything can talk to everything else – though tens of hundreds of people have worked to enhance the work originally done by Mockapetris, who is now chief scientist and chairman of the board at Nominum, a commercial DNS outfit. "If you send an email, you expect the system to figure out how to get it to where it's going – whichever one of the 200 million domains that might be – and by and large, it all works."